The invention relates generally to cooling devices for transferring heat from an item to be cooled, such as electronic components, for example. More, specificially, the present invention relates to such devices wherein a phase change in a cooling medium, from the liquid to the gaseous phase, is employed to extract heat from the item to be cooled. Sufficient control of temperatures in components of a system is frequently very critical to the proper operation of the system, but is often difficult to achieve. Such temperature control is especially critical in electronic components that are subjected to severe environments, such as those frequently found in automotive electronic applications. Recent trends in automotive design have further complicated this problem in that electronic components are now being located closer to other system components, such as the engine or power train, in order to obtain various advantages in vehicle design, assembly, and servicing operations.
In order to address the temperature control problems discussed above, various systems have been proposed, but most of which which suffer from one or more disadvantages. For example, many of the components or systems used to attain the required degree of temperature control depend upon an external power source for their operation, are inordinately expensive or complex to manufacture, install, or service, or are not effective over widely varying ambient conditions. The present invention, however, seeks to overcome these disadvantages by providing a two-phase cooling apparatus capable of providing increased reliability, stable temperature control, an internal heat accumulation function, and no need for external power requirements.
According to the present invention, a two-phase cooling device for transferring heat from an item to be cooled includes a sealed enclosure defined by at least first and second thermally conductive walls spaced apart from one another and by side walls interconnecting the first and second thermally conductive walls. One of the thermally conductive walls is adapted for interconnection in a thermally conductive relationship with the item desired to be cooled.
A wick structure is disposed within the generally hollow interior of the sealed enclosure, and the wick structure includes a first wick portion extending along at least a substantial portion of the thermally conductive wall to which the item to be cooled is interconnected, as well as at least one second wick portion protruding transversely from the first wick portion. The second wick portion has a free end extending generally adjacent the second thermally conductive wall, with the second wick portion or portions being at least partially submerged within a thermally conductive liquid disposed within the hollow interior of the sealed enclosure.
The thermally conductive liquid (examples of which can be glycol, water, ammonia, acetone, methylalcohol, or a mixture thereof, or other suitable substances known to those skilled in the art), is capable of being transported through the wick portions, with the liquid being evaporated by the transfer of heat from the item to be cooled into the first wick portion. The vapor is then condensed on various surfaces such as those defined by internal components, as well as the surface of the thermally conductive liquid.
Preferably the two-phase cooling device also includes at least one partition extending through the interior of the enclosure to at least partially divide the interior into a heat intake chamber and a heat rejection chamber, with the partition having at least one partition opening extending therethrough in order to provide fluid communication between the heat intake and rejection chambers. In other embodiments, however, a pair of spaced-apart partitions are provided in order to define an intermediate chamber between the heat intake chamber and the heat rejection chamber. Such intermediate chamber, which is spaced apart from the side walls in order to provide the above-mentioned opening, can be evacuated or filled with a thermally conductive, high-boiling-point liquid in order to provide for an enhanced heat accumulation capability.
These and other objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.